三峡工程库水位降与红层岸坡稳定性变化的响应关系研究

三峡工程水库运营中，库水位在145～175 m间周期性变化必将引起岸坡地下水位的波动，从而导致岸坡稳定性的响应变化。为此，根据布辛涅斯克非稳定渗流微分方程，采用多项式拟合初始浸润线，求得了库水位匀速下降和定幅度下降时岸坡的浸润线方程；在运用剩余推力法求解岸坡稳定性时考虑了对应的渗透力。以千将坪滑坡北东侧的红层岸坡为实例，分别考虑库水位由156 m匀速下降至145 m和库水位由156 m定幅度下降时岸坡的稳定性。结果表明：库水位以不同速度匀速下降时，降速越大，稳定性系数下降速率越大；地下水的时间滞后效应随降速的增大而明显延迟，但随着库水位的下降，滞后效应将达到一个最大值；库水位定幅度下降时，降幅与岸坡稳定性系数关系曲线呈现下降速率不同的3段；对于千将坪滑坡北东侧的红层岸坡在库水位匀速下降时，其临界降速为1.2 m/d，在库水位定幅度下降时，其临界单次降幅不超过6.0 m。研究结果对三峡工程库区类似岸坡地质灾害预警预报具有一定的指导意义。

The response research of decline of Three Gorges Reservoir water level on change of red beds bank slope stability

The bank slope always responds well to its stability when the Three Gorges Reservoir water level fluctuates. A research was done to gain the equation of saturation line when the reservoir water level declines from 156m to145m in a steady speed and from 156m to a height in a steady height. Multinomial fitting was introduced to work out the equation for the initial saturation line. As a typical example, the bank slope of red beds to the northeast of Qianjiangping slope was analyzed and the stability coefficient of the bank slope was calculated when the reservoir water level declines. The results show that when the reservoir water level declines in a steady speed, the higher the speed is, the bigger the deducing rate of the stability coefficient is; the higher the declining speed is, the more remarkable the hysteresis of the groundwater is, but the hysteresis will reach to a peak as the water level declines; when the reservoir water level declines in a steady height, the relation curve between the height and the stability coefficient presents three segments with different declining ratios. As to the slope northeast to Qianjiangping landslide, the critical declining velocity is 1.2 meter per day while the reservoir water declines in a steady speed. When the reservoir water declines in steady height, the critical condition is that the single declining height must not beyond 6 meters. It is significant to guide the prewarning and forecasting of geologital disaster which is similar to the bank slope in the Three Gorges Reservoir.